Trouble with canon 450d

[teztwister]

I dont know if this is the right place to post this thread but here gose,

I have just started imaging with a Canon 450D and a Orion ed80, but my concern is with the 450D.I have never imaged with a DSLR before so i dont know any different , my queriy is when i take a 30 second exposure it looks quite dark but when i start taking say exposures of 90 seconds , 120 seconds or 150 seconds the picture starts to go really light and red and gets even worse as the exposure time lenghthens .

I have downloaded 2 pictures . One is 45 seconds at iso 1600 and the other is 120 seconds at iso 1600

Is this normall , if it is then is there any way to overcome the problem like a filter

[themos]

Before you fork out for a Lumicon Deep Sky 2" filter, say, consider that your unprocessed images need some massaging to look "nice". That's where the "dark" and "flat" frames come in. But even some basic image processing will make the image more presentable. Here it is with some DBE (dynamic background extraction) in PixInsight LE.

[teztwister]

So it is normall then, an there's nothing WRONG with the camera, thinking about it i do live i a light polluted aera so it could just be the dreaded skyglow

Yes it's a big learning curve to produce nice astrophotos,

Is that all you did to the picture just some DBE (dynamic background extraction)

This is probably my best to date no darks or anything else

[themos]

Yes, that's all. You can get similar or better results by feeding the original file (did you shoot RAW or JPEG, I recommend RAW format) to the Canon DPP program that's in your CDROM. There you can play with "Levels" and "Curves" (they are explained in the manual for DPP).

[teztwister]

I saved the images in both raw and jpeg , it just something i read and it said to save in both formats , but to tell you the truth i've never used the jpeg file's.

So before putting the files in DSS play around in DPP first to get them looking better

[MishMich]

I have an EOS1000D and I get this on longer exposures, and because the light pollution is worse to the West, when I am tracking something South moving West, I get gradients too, where it is worse at the bottom right than the top left on some of my frames. It is a pain, but I guess it could be called normal, depending where you live. Do you notice whether the RAW files are any better? I find the JPEG's automatic processing makes them look worse. I did find stacking RAW in DSS seemed to help, until I started doing longer exposures that brought in the gradients - then I was pointed to DPP. It is quite powerful, you can select a batch of RAW files and apply the same action to all of them before stacking - very useful. I am very grateful that somebody pointed me to that.

M.

[dph1nm]

After 2mins (on the outskirts of Durham) the red channel on my 1000D is about 200/255. So, yes, this is normal.

Is it a problem? Well, it depends. I am limited to this time by tracking errors anyway (no autoguiding)., so I don't have much choice., but the main problems I find are:

* Stars get saturated in the red channel very quickly. so you loose star colours (or get weird ones).

* The noise in the red channel tends to be higher than B or G, which cosmetically doesn't always help the appearance.

* It is more difficult to flatten the background

* It is a pain to store and process all those short exposures!

NigelM

[harry page]

Hi

I do not a DSLR , but I know its a common problem with them

I have processed some images from dslr cameras for people with pixinsight 1.5 and you might be interested in the video on how its was done.

http://www.harrysastroshed.com/pixinsighthomeinter.html

Look at bottom " the sword of orion "

The video does show how to get rid of that red cast

Harry

[jgs001]

Yep pretty normal... I get similar sorts of results with my 450d on longer exposures (my LP is actually quite low). A filter deals with it well... the SW LPR filter is cheap as chips and does a fairly good job. The CLS clip filter does an absolutely stunning job at removeing LP but it costs so much more than the SW filter. The filters will help reduce the effects.

[MickyWay]

You might try to lower your ISO to 200 or 400 ?

Regards,

[themos]

In DPP, you can use the Shadows/Highlight menu entry to see if there are regions (star centres most likely) that are saturated. If they are (and you care about that part of the image) you should reduce the ISO setting so that the pixels don't saturate in that exposure time.

[teztwister]

Thanks for all the answers guys, I have got a Meade 4000 nebular filter would this do the job OR would you recomend getting a CLS clip. can it be a 1.25" or does it have to be a 2" filter

I will give it a go but i've only got a few subs to play around with, some of pleiades and some of Orion (this weather is a nightmare).

Can you give me an idear of the settings, exposure time and how many subs i would need to take to get the nebulosity out in pleiades (Orion ED80 & 450D), would say 10 x 30 seconds at iso 800 be any good or would i need more subs or would i need longer exposure time or both, and with the darks do i take the same amount of dark as light frams, 10 dark 10 light.

Cheers Tez

[LukeSkywatcher]

There really is no fixed formula for getting the best results. It really all depends on how badly LP in your area is. Takes dozens of images using different ISO settings,exposure times,WB etc and see which one works best from your location. When you are happy with the image then you know to take multiple images and stack them.

[dph1nm]

Can you give me an idear of the settings, exposure time and how many subs i would need to take to get the nebulosity out in pleiades (Orion ED80 & 450D), would say 10 x 30 seconds at iso 800 be any good

I should think so. Here is 20mins ISO800 (30 sec subs) from my same light polluted Durham site with a 4in refractor and a 1000D (after processing to remove the light pollution I hasten to add):

NigelM

[teztwister]

WOW !!!!! and thats just with 40 x 30 second exposures

[LukeSkywatcher]

WOW !!!!! and thats just with 40 x 30 second exposures

My thoughts exactly.